实际上，你不需要使用Sinon来测试去抖动，Jest可以在JavaScript代码中模拟所有的计时器。
看看下面的代码（它是TypeScript，但你可以很容易地把它翻译成JavaScript）：

import * as _ from 'lodash';

// Tell Jest to mock all timeout functions
jest.useFakeTimers();

describe('debounce', () => {

    let func: jest.Mock;
    let debouncedFunc: Function;

    beforeEach(() => {
        func = jest.fn();
        debouncedFunc = _.debounce(func, 1000);
    });

    test('execute just once', () => {
        for (let i = 0; i < 100; i++) {
            debouncedFunc();
        }

        // Fast-forward time
        jest.runAllTimers();

        expect(func).toBeCalledTimes(1);
    });
});

更多信息：* 一个月一次 *

如果在代码中这样做：

import debounce from 'lodash/debounce';

myFunc = debounce(myFunc, 300);

如果你想测试函数myFunc或者调用它的函数，那么在测试中你可以使用jest模拟debounce的实现，让它只返回你的函数：

import debounce from 'lodash/debounce';

// Tell Jest to mock this import
jest.mock('lodash/debounce');

it('my test', () => {
    // ...
    debounce.mockImplementation(fn => fn); // Assign the import a new implementation. In this case it's to execute the function given to you
    // ...
});

来源：https://gist.github.com/apieceofbart/d28690d52c46848c39d904ce8968bb27

您可能需要检查debouncer函数中的逻辑：

• timeout将始终由最后一条if()语句设置
• this将总是undefined，因为箭头函数使用“封闭词法上下文的this值”，并且debouncer()被设计成用作独立函数。

话虽如此，听起来你真实的的问题是关于测试去抖函数。

测试去抖功能

您可以通过使用模拟跟踪函数调用和伪计时器模拟时间的流逝来测试函数是否去抖。
下面是一个简单的示例，使用debounce()从Lodash去抖函数的Jest Mock Function和Sinon fake timers：

const _ = require('lodash');
import * as sinon from 'sinon';

let clock;

beforeEach(() => {
  clock = sinon.useFakeTimers();
});

afterEach(() => {
  clock.restore();
});

test('debounce', () => {
  const func = jest.fn();
  const debouncedFunc = _.debounce(func, 1000);

  // Call it immediately
  debouncedFunc();
  expect(func).toHaveBeenCalledTimes(0); // func not called

  // Call it several times with 500ms between each call
  for(let i = 0; i < 10; i++) {
    clock.tick(500);
    debouncedFunc();
  }
  expect(func).toHaveBeenCalledTimes(0); // func not called

  // wait 1000ms
  clock.tick(1000);
  expect(func).toHaveBeenCalledTimes(1);  // func called
});

我喜欢这个类似的版本更容易有失败：

jest.useFakeTimers();
test('execute just once', () => {
    const func = jest.fn();
    const debouncedFunc = debounce(func, 500);

    // Execute for the first time
    debouncedFunc();

    // Move on the timer
    jest.advanceTimersByTime(250);
    // try to execute a 2nd time
    debouncedFunc();

    // Fast-forward time
    jest.runAllTimers();

    expect(func).toBeCalledTimes(1);
});

使用现代的假计时器（Jest 27已经默认了），你可以更简洁地测试它：

import debounce from "lodash.debounce";
describe("debounce", () => {
  beforeEach(() => {
    jest.useFakeTimers("modern");
  });
  afterEach(() => {
    jest.useRealTimers();
  });
  it("should work properly", () => {
    const callback = jest.fn();
    const debounced = debounce(callback, 500);
    debounced();
    expect(callback).not.toBeCalled();

    jest.advanceTimersByTime(100);
    debounced();
    expect(callback).not.toBeCalled();

    jest.advanceTimersByTime(499);
    expect(callback).not.toBeCalled();

    jest.advanceTimersByTime(1);
    expect(callback).toBeCalledTimes(1);
  });

  it("should fire with lead", () => {
    const callback = jest.fn();
    const debounced = debounce(callback, 500, { leading: true });
    expect(callback).not.toBeCalled();
    debounced();
    expect(callback).toBeCalledTimes(1);

    jest.advanceTimersByTime(100);
    debounced();
    expect(callback).toBeCalledTimes(1);

    jest.advanceTimersByTime(499);
    expect(callback).toBeCalledTimes(1);

    jest.advanceTimersByTime(1);
    expect(callback).toBeCalledTimes(2);
  });
});

你可以把它实现为一个状态钩子，像这样去抖......

import debounce from "lodash.debounce";
import { Dispatch, useCallback, useState } from "react";

export function useDebouncedState<S>(
  initialValue: S,
  wait: number,
  debounceSettings?: Parameters<typeof debounce>[2]
): [S, Dispatch<S>] {
  const [state, setState] = useState<S>(initialValue);
  const debouncedSetState = useCallback(
    debounce(setState, wait, debounceSettings),
    [wait, debounceSettings]
  );
  return [state, debouncedSetState];
}

并测试为

/**
 * @jest-environment jsdom
 */
import { act, render, waitFor } from '@testing-library/react';
import React from 'react';
import { useDebouncedState } from "./useDebouncedState";

describe("useDebounceState", () => {
  beforeEach(() => {
    jest.useFakeTimers("modern");
  });
  afterEach(() => {
    jest.useRealTimers();
  });
  it("should work properly", async () => {
    const callback = jest.fn();
    let clickCount = 0;
    function MyComponent() {
      const [foo, setFoo] = useDebouncedState("bar", 500);
      callback();
      return <div data-testid="elem" onClick={() => { ++clickCount; setFoo("click " + clickCount); }}>{foo}</div>
    }
    const { getByTestId } = render(<MyComponent />)
    const elem = getByTestId("elem");

    expect(callback).toBeCalledTimes(1);
    expect(elem.textContent).toEqual("bar");

    jest.advanceTimersByTime(100);
    elem.click();
    expect(callback).toBeCalledTimes(1);
    expect(elem.textContent).toEqual("bar");

    jest.advanceTimersByTime(399);
    expect(callback).toBeCalledTimes(1);
    expect(elem.textContent).toEqual("bar");

    act(() => jest.advanceTimersByTime(1));

    await waitFor(() => {
      expect(callback).toBeCalledTimes(2);
      expect(elem.textContent).toEqual("click 1");
    });

    elem.click();
    await waitFor(() => {
      expect(callback).toBeCalledTimes(2);
      expect(elem.textContent).toEqual("click 1");
    });
    act(() => jest.advanceTimersByTime(500));
    await waitFor(() => {
      expect(callback).toBeCalledTimes(3);
      expect(elem.textContent).toEqual("click 2");
    });

  });
});

源代码可从https://github.com/trajano/react-hooks-tests/tree/master/src/useDebouncedState获得

以下是我的3项基本测试：

测试“去抖”逻辑有一些基本原理。
请注意，所有测试都是 async，因为测试的本质本身就是异步的。

import debounce from 'lodash.debounce'

const delay = ms => new Promise(resolve => setTimeout(resolve, ms))

test('called repeatedly', async () => {
  const DELAY = 100;
  let callCount = 0;
  const debounced = debounce(() => ++callCount, DELAY)

  for( let i = 4; i--; )
    debounced()
 
  await delay(DELAY)
  expect( callCount ).toBe(1) 
})

test('called repeatedly exactly after the delay', async () => {
  const DELAY = 100;
  let callCount = 0, times = 3;
  const debounced = debounce(() => ++callCount, DELAY)

  for( let i = times; i--; ) {
    debounced()
    await delay(DELAY) 
  }
 
  await delay(DELAY * times)
  expect( callCount ).toBe(3) 
})

test('called repeatedly at an interval small than the delay', async () => {
  const DELAY = 100;
  let callCount = 0, times = 6;
  const debounced = debounce(() => ++callCount, DELAY)

  for( let i = times; i--; ) {
    debounced()
    await delay(DELAY/2) 
  }
 
  await delay(DELAY * times)
  expect( callCount ).toBe(1) 
})

这些测试由我编写，并非取自lodash debounce tests source code

另一种方法是刷新去抖函数，使其立即执行：

test('execute just once', () => {
    const func = jest.fn();
    const debouncedFunc = debounce(func, 500);

    // Execute for the first time
    debouncedFunc();
    debouncedFunc.flush();

  
    // try to execute a 2nd time
    debouncedFunc();
    debouncedFunc.flush();

    expect(func).toBeCalledTimes(1);
});

花了很多时间来弄清楚...终于成功了...。

jest.mock('lodash', () => {
    const module = jest.requireActual('lodash');
    module.debounce = jest.fn(fn => fn);
    return module;
});